Magnetic head and magnetic storage apparatus using the same

ABSTRACT

It is the object of the invention to provide a magnetic head and a magnetic storage apparatus using the magnetic head provided with a signal reproducing means which is capable of using the same signal processing circuit as used for the conventional longitudinal magnetization film type recording medium even when a perpendicular magnetization film type recording medium is used. Because the present invention renders the reproducing signal generated from a perpendicular magnetization film Gaussian shaped (Lorentzian pulse), the same signal processing circuit as used for the conventional longitudinal magnetization film type recording medium can be used. To accomplish this object, in the reproducing means which is the component of the information reproducing component of the magnetic head, the first spin valve element and the second valve element are piled up, the magnetization direction of pinned layers of both elements is prescribed so as to be antiparallel each other, and lead electrodes of both elements are connected so as to be common. When two spin valve elements are piled up to compose a reproducing means, the first spin valve element is structured so as to have an Ru film between the first ferromagnetic film and the second ferromagnetic film and so as to have a Cu film between the second ferromagnetic film and the third ferromagnetic film, and the second spin valve element is structured so as to have a Cu film between the fourth ferromagnetic film and the fifth ferromagnetic film. These two elements are piled up with interposition of a desired spacer film adjacently.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a magnetic storage apparatus used forcomputers and information processing apparatuses, and more particularlyrelates to a magnetic head and a magnetic storage apparatus suitable fora perpendicular magnetic recording medium obtained realizing a highdensity recording.

[0003] 2. Description of the Prior Art

[0004] Information processing apparatus employs mainly semiconductormemory and magnetic memory as their storage apparatus. Semiconductormemory is used mainly for the internal storage apparatus in view ofaccess time, and magnetic memory is used mainly for external storageapparatus in view of large capacity and non-volatility.

[0005] Recently, magnetic disk and magnetic tape have been mainly usedas magnetic memory. A recording medium used for these magnetic memorycomprises an Al substrate or resin tape on which a magnetic thin film isformed. To record magnetic information on the recording medium, afunctional component having electromagnetic conversion function is used.To reproduce magnetic information, a functional component which utilizesmagnetoresistive phenomenon, giant magnetoresistive phenomenon, orelectromagnetic induction phenomenon is used. The functional componentis incorporated in an input/output unit so-called a magnetic head.

[0006] A magnetic head and a recording medium are moved relatively, andhave a function to record magnetic information on the arbitrary positionof the medium and to reproduce electrically magnetic information asrequired.

[0007] As shown in FIG. 2, a magnetic head comprises, for example, arecording component 21 for recording magnetic information and areproducing component 22 for reproducing magnetic information.

[0008] The recording component 21 comprises a coil 26 and magneticallycoupled magnetic poles 27 and 28 located so that the coil 26 issandwiched therebetween.

[0009] The reproducing component 22 comprises a magnetoresistive effectunit 23 and an electrode 29 for supplying a constant current to themagnetoresistive effect unit 23 and for detecting resistance change.

[0010] Between the recording component 21 and the reproducing component22, a magnetic shield layer 28 (served also as the write pole) isprovided. These functional components are formed on a magnetic head body30 through a primary layer.

[0011] The example shown in FIG. 2 utilizes electromagnetic conversionfunction for recording and utilizes magnetoresistive effect forreproducing. However, the reproduction of magnetic information may beperformed by detecting electromagnetic induction current induced in acoil provided in a recording component. In this case one component isserved for both recording and reproducing.

[0012] The performance of a storage apparatus depends on theinput/output operation speed and storage capacity, as a result, shortaccess time and large storage capacity are essential to render theproduct competitive. Recently small sized storage apparatus have beendeveloped in response to the request for compact information apparatus.To satisfy this request, development of a magnetic memory device forrecording and reproducing much magnetic information in and from a singlesheet of recording medium is important.

[0013] To satisfy this request, it is required to increase the recordingdensity of a magnetic memory device. To increase the recording density,it is required to miniaturize the size of domain which is the source ofmagnetic information. It is required to increase the frequency ofrecording current supplied to the coil 26 shown in FIG. 2 and to designthe width W of recording magnetic pole 27 narrow.

[0014] According to the examination of the inventors, a condition that arecording pole width W of 2.5 μm and a recording frequency of about 90MHz realized a recording density of 2 Gb/in² class. However, it wasfound that more increased density caused a problem and revealed thelimitation of high density recording.

[0015] Heretofore, magnetic films called as longitudinal media ofin-plane magnetization direction have been used as recording media. Inan in-plane medium, boundary between domains is mainly magnetized, themagnetization is read out by detecting field intensity. Because themagnetization is concentrated, a signal of Gaussian shape (Lorentzianshape) pulse signal is outputted. Since frequency band contained in asignal is narrow, it is less susceptible to the deterioration of signalquality due to neighboring signal. Therefore, signals are processedeasily thereafter.

[0016] However, thermal fluctuation of magnetization is inevitableproblem in development of high density recording using an in-planemedium. The thermal fluctuation is due to thermal fluctuation ofmagnetization in a recording medium, and the thermal fluctuation iscaused with increasing miniaturization of domain because thedemagnetizing effect of neighboring domain becomes remarkable andmagnetization direction becomes unstable.

[0017] According to experiments conducted by the inventors, it wasconfirmed that domain could be erased due to thermal fluctuation whendensity was increased as high as to about 400 kbPI (bits per inch) inthe circular direction and about 26 kTPI (tracks per inch) in the radiusdirection.

[0018] The perpendicular magnetic recording is known as a technology forpreventing the problem. Because demagnetization of neighboring domainfunctions so that fluctuation width of magnetization due to thermalfluctuation is decreased, the domain erasing phenomenon due to thermalfluctuation is less susceptible. Therefore, the perpendicular magneticrecording is expected to be the high density recording technology of thefuture.

[0019] However, because magnetic charges are distributed on the mediumsurface in the perpendicular magnetic recording, if magnetization isreproduced using a reproducer used for detecting field intensity of aconventional longitudinal medium as shown in FIG. 2, square wave(dipulse) is detected depending on domain width. Such square waverequires complex signal processing because of wide band. Such complexsignal processing requires use of a complex electric circuit. Therefore,it is difficult to realize an inexpensive and high speed apparatus, andas a result, this problem is one of the reasons of slowcommercialization of the perpendicular magnetic recording.

SUMMARY OF THE INVENTION

[0020] The above-mentioned problem will be solved if output signalsobtained from perpendicular media are of Gaussian shape similarly toconventional longitudinal media.

[0021] Accordingly, it is the object of the present invention to providea magnetic head and a magnetic recording apparatus using the magnetichead having a novel reproducing means which is capable of outputtingreproducing signal obtained from a perpendicular magnetic medium asGaussian shape pulse signal. The present invention can realizes highspeed and high density magnetic recording apparatus which utilizesperpendicular magnetic recording method.

[0022] In order to realize the above-mentioned object, the magnetic headand the magnetic recording apparatus using the magnetic head of thepresent invention use means described hereinafter.

[0023] The first means uses a perpendicular magnetization film having aneasy magnetization axis perpendicular to the direction of the filmsurface, and the first means is provided with at least a magnetic headhaving a function for recording and reproducing information.Particularly in the magnetic head, a reproducing means for havingreproducing function of information is provided with piled up two spinvalve elements with a pinned layers having magnetization directiondifference of about 180 degrees, and recorded information is reproducedfrom the perpendicular magnetization film.

[0024] In detail, the object of the present invention is accomplished byproviding a magnetic recording apparatus provided with a perpendicularmagnetic recording medium having an easy magnetization axis in thedirection perpendicular to the longitudinal surface, and a magnetic headhaving both recording and reproducing function of information, whereinthe magnetic head is structured with a reproducing means comprisingpiled two (the first and second) spin valve elements having at least amagnetoresistive elements for performing reproducing function, and themagnetization direction of pinned layers which are a components of eachspin valve element is different by about 180 degrees each other.

[0025] Both ends of two (first and second) spin valve elementsrespectively provided with a magnetoresistive element is connectedcommonly and an electrode is provided to each terminal, and operation ofread out (reproducing) means is performed by connecting a constantvoltage power source or constant current power source to an electrode.

[0026] Preferably pinned layers of the piled two spin valve elementscomprises respectively an antiferromagnetic film, and a blockingtemperature difference of the respective antiferromagnetic films isprescribed to be 20° C. or larger. The blocking temperature will bedescribed hereinafter.

[0027] Alternatively, pinned layers of the piled two spin valve elementcomprise a high coercive force film, and a coercive force difference ofthe respective high coercive force films is prescribed to be 100 Oe orlager.

[0028] A current terminal of the first spin valve element and a currentterminal of the second spin valve element are connected commonly, and anelectrode is provided on the common point. Thereby two elements functionas a single device.

[0029] Alternatively, the first spin valve element and the second spinvalve element are maintained electrically insulated, connected so thatoutput from the elements is in differential mode, and supplied with acurrent.

[0030] In the above-mentioned case, a dual spin valve element having thefirst spin valve element and the second spin valve element provided witha single oxide antiferromagnetic film inserted therebetween isstructured.

[0031] The above-mentioned reproducing means is incorporated in amagnetic head slider, and provided partially on an air bearing surfaceat least near a perpendicular magnetic recording medium.

[0032] In the above-mentioned reproducing means, the respective spinvalve elements are piled up closely, and a soft magnetic pattern isprovided between these spin valve elements on the side distant from theair bearing surface. The soft magnetic pattern forms a magnetic circuitfrom the first spin valve element to the second spin valve element.

[0033] The second means to accomplish the above-mentioned object is amagnetic recording apparatus comprising a perpendicular magneticrecording medium having an easy magnetization axis in the directionperpendicular to the film surface and a magnetic head having bothfunctions for recording and reproducing information. The reproducingfunction of the magnetic head is given by a reproducing means providedwith the first spin valve element and the second spin valve elementpiled up with interposition of a spacer film which spin valve elementsat least comprise a magnetoresistive element, the first spin valveelement comprises the first ferromagnetic film, the first non-magneticmedium layer, the second ferromagnetic film, the second non-magneticfilm, and third ferromagnetic film placed one on another in this orderor in inverse order, and functions thereby so that the firstferromagnetic film and the second ferromagnetic film exert exchangeinteraction each other so as to direct the magnetization direction ofthe respective ferromagnetic films in inverse direction, and thedifference in magnetization direction between the second ferromagneticlayer and the third ferromagnetic layer generates magnetoresistiveeffect. The second spin valve element comprises the fourth ferromagneticfilm, the third non-magnetic medium layer, and fifth ferromagnetic filmplaced one on another in this order or in inverse order, and functionsthereby so that the difference in magnetization direction between thefourth ferromagnetic film and the fifth ferromagnetic film generatesmagnetoresistive effect.

[0034] Both ends of two (first and second) spin valve elementsrespectively provided with a magnetoresistive element is connectedcommonly and an electrode is provided to each common point, andoperation of read out (reproducing) means is performed by connecting aconstant voltage power source or constant current power source to anelectrode.

[0035] In the structure of the spin valve element, the firstnon-magnetic medium layer comprises a layer with a thickness of 1.5 nmor thinner consisting of any one of metal layers selected from a groupof Ru, Rh, Ir, Cr, and Cu or consisting of an alloy containing some ofthese metals. The first non-magnetic medium layer is sandwiched betweenferromagnetic layers to generate strong antiferromagnetic exchangeinteraction between these ferromagnetic layers. As a result, themagnetization direction of the first ferromagnetic layer and themagnetization direction of the second ferromagnetic layer are always inantiparallel relation each other.

[0036] The above-mentioned second non-magnetic medium and thirdnon-magnetic medium layer comprise a Cu layer.

[0037] The product of the film thickness and saturation magnetization ofthe first ferromagnetic film is prescribed to be larger than the productof the film thickness and saturation magnetization of the secondferromagnetic film.

[0038] Further, a spacer film for separating the first spin valveelement from the second spin valve element is sandwiched between thethird ferromagnetic film and the fourth ferromagnetic film, and thethird ferromagnetic film and the fourth ferromagnetic film are bothcomprise a soft magnetic film.

[0039] The magnetization of the first ferromagnetic film and the fifthferromagnetic film are prescribed to be in the same direction.

[0040] The above-mentioned first ferromagnetic film and the fifthferromagnetic film are structured so that the magnetization direction isspecified by the antiferromagnetic film or hard magnetic film which isin contact with these ferromagnetic films respectively.

[0041] The third means to accomplish the above-mentioned object has astructure in which, for example, the first spin valve element having anRu film provided between the first ferromagnetic film and the secondferromagnetic film, and having a Cu film provided between the secondferromagnetic film and the third ferromagnetic film, and the second spinvalve element having a Cu film provided between the fourth ferromagneticfilm and the fifth ferromagnetic film and having an Ru film providedbetween the fifth ferromagnetic film and the sixth ferromagnetic filmare provided with interposition of a desired spacer film adjacently, thereproducing function component having the above-mentioned structure isused for reproducing information.

[0042] In detail, the third means is a magnetic recording apparatusprovided with a perpendicular magnetic recording medium having an easymagnetization axis perpendicular to the film surface direction and amagnetic head having both functions for recording and reproducinginformation. The reproducing function of the magnetic head is given by areproducing means provided with the first spin valve element and thesecond spin valve element piled up with interposition of a spacer filmwhich spin valve elements at least comprise a magnetoresistive element.The first spin valve element has the first nonmagnetic medium layerbetween the first ferromagnetic film and the second ferromagnetic film,and has the second non-magnetic medium layer between the secondferromagnetic film and the third ferromagnetic film, and the second spinvalve element has the third non-magnetic medium layer between the fourthferromagnetic film and the fifth ferromagnetic film, and has the fourthnon-magnetic medium layer between the firth ferromagnetic film and thesixth ferromagnetic film.

[0043] An electrode is provided respectively on the both ends of the twospin valve elements, and operation of read out (reproducing) means isperformed by connecting a constant voltage power source or constantcurrent power source to an electrode.

[0044] Preferable structure is described herein under. The firstnon-magnetic medium layer and the fourth non-magnetic medium layerrespectively comprise a layer consisting of any one of metal layersselected from a group of Ru, Rh, Ir, Cr, and Cu or consisting of analloy containing some of these metals.

[0045] The above-mentioned second non-magnetic medium layer and thirdnon-magnetic medium layer comprise respectively a Cu layer.

[0046] The film thickness of the first ferromagnetic film is prescribedto be thicker than the film thickness of the ferromagnetic film, and thefilm thickness of the fifth ferromagnetic film is prescribed to bethicker than the film thickness of the sixth ferromagnetic film.

[0047] A spacer film for separating the first spin valve element fromthe second spin valve element is provided between the thirdferromagnetic film and the fourth ferromagnetic film, and the thirdferromagnetic film and the fourth ferromagnetic film respectivelycomprise a soft magnetic film.

[0048] The magnetization direction of the first ferromagnetic film andthe fifth ferromagnetic film are respectively structured so as to bedirected in the same direction.

[0049] Further, the magnetization direction of the first ferromagneticfilm and sixth ferromagnetic film is specified respectively by anantiferromagnetic film or hard magnetic film which are respectively incontact with these ferromagnetic films.

BRIEF DESCRIPTION OF THE DRAWING

[0050]FIG. 1A is a perspective view for illustrating the structure of areproducing means of one example of the present invention.

[0051]FIG. 1B is a sectional view of the reproducing means taken alongthe line α in FIG. 1A.

[0052]FIG. 1C is a sectional view of the reproducing means taken alongthe line β in FIG. 1A.

[0053]FIG. 1D is a sectional view for illustrating piling up of spinvalve elements 33 and 34 taken along the line β in FIG. 1A.

[0054]FIG. 2 is a perspective view for illustrating a reproducingcomponent 21 and recording component 22 of a conventional magnetic head.

[0055]FIG. 3 is a plan view of a magnetic recording apparatus providedwith a reproducing means to which the present invention is applied as areproducing component of a magnetic head.

[0056]FIGS. 4A and 4B are diagrams for describing the principle of thehead using dual MR as a reproducing means.

[0057]FIG. 5A is a perspective view for illustrating the structure of areproducing means of the second example of the present invention.

[0058]FIG. 5B is a sectional view for illustrating piling up of piled uptwo spin valve elements 33 and 34 in FIG. 5A.

[0059]FIG. 5C is a diagram of a circuit for processing signal outputtedfrom piled up two spin valve elements 33 and 34 in FIG. 5A.

[0060]FIG. 6A, FIG. 6B, and FIG. 6C are schematic diagrams fordescribing operational principle of the present invention comprisingpiled up two spin valve elements 33 and 34.

[0061]FIG. 7A and FIG. 7B are diagrams for describing operationalprinciple of a reproducing means of one example of the presentinvention.

[0062]FIG. 8 is a diagram for describing operational principle of areproducing means of another example of the present invention.

[0063]FIG. 9 is a sectional view of a spin valve element which is acomponent of the reproducing component of another example of the presentinvention.

[0064]FIG. 10A and FIG. 10B are diagrams for describing magnetization oftwo spin valve elements 33 and 34.

[0065]FIG. 11A1 and FIG. 11A2 are diagrams for describing principle forchanging pinned layer magnetization antiparallel of the spin valveelement 34.

[0066]FIG. 11B1 and FIG. 11B2 are diagrams for describing principle forchanging pinned layer magnetization antiparallel of the spin valveelement 33.

[0067]FIG. 12A and FIG. 12B are diagrams for describing operationalprinciple of a reproducing component of the present invention.

[0068]FIG. 13 is a sectional view for illustrating a reproducing meanscomprising a piled up two spin valve elements of another example of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Example

[0069] A typical structure of a reproducing component of a magnetic headto which a magnetic recording apparatus of the present invention will bedescribed hereinafter with reference to FIG. 1A to FIG. 1D.

[0070]FIG. 1A is a schematic diagram of the reproducing component(corresponds to the reproducing component shown in FIG. 2). Thereproducing component comprises a magnetoresistive element 32 andelectrodes 31. In the present invention, a giant magnetoresistiveelement or conventional magnetoresistive element may be used as themagnetoresistive element 32. An example in which a giantmagnetoresistive element is used is described in this example.

[0071]FIG. 1B shows a sectional structure taken along the line α in FIG.1A, and FIG. 1C shows a sectional structure taken along the line β inFIG. 1A. As shown in FIG. 1B and FIG. 1C, the first giantmagnetoresistive element 33 and the second giant magnetoresistiveelement 34 are piled up, and a non-magnetic film is provided between thegiant magnetoresistive elements 33 and 34. Magnetic patterns 35 havinghigh coercive force are provided on both ends of the giantmagnetoresistive elements 33 and 34 to change the soft magnetic layerwhich is a component of the giant magnetoresistive element to a singledomain and to arrange magnetization in the same direction.

[0072] The magnetization direction of the magnetic patterns 35 is inparallel to the line α like the conventional longitudinal medium. Theelectrodes 31 are located on the magnetic patterns 35, and structured soas to supply a current to two giant magnetoresistive elements 33 and 34in the same direction.

[0073] In the structure described hereinbefore, the structure is novelin that two functional thin films 33 and 34 corresponding to giantmagnetoresistive elements are piled up with interposition of thenon-magnetic film 36 and in that common electrodes 31 are connected tothese two functional thin films.

[0074] The electric resistance of each functional thin film changesdepending on the field intensity (perpendicular field component;parallel field component to the line β shown in FIG. 1A) at the positionwhere the functional thin film is located. The change is detected as thechange of the voltage between both ends by supplying a constant currentto the functional thin film. Alternatively, the change can be detectedas the change of the current by supplying a constant voltage.

[0075] By using functional thin films located at positions distantspatially each other, the field intensity at the positions distantspatially each other can be measured simultaneously. Therefore, bydetecting the field intensity difference as an output difference, thefield gradient between the positions distant spatially each other can bemeasured.

[0076] First, to detect the field intensity difference at the positionsdistant spatially each other, two giant magnetoresistive elements arestructured to have a spin valve element structure in this example. Thedetailed structure is described with reference to FIG. 1D.

[0077] An under layer film (Hf: 5 nm) 41 is deposited, and successivelya soft magnetic film (free layer: NiFe: 6 nm) 42, a non-magnetic film(Cu: 3 nm) 43, a pinned layer (pinned layer: NiFe: 3 nm) 44, and anantiferromagnetic film (Fe—Mn: 10 nm) are deposited, and these filmsconstitute the first spin valve element (giant magnetoresistive elementor functional thin film in a broader sense of the term) 34.

[0078] Similarly, the second spin valve element 33 is also formed bydepositing a under layer film (Hf: 5 nm) 46, a soft magnetic film (freelayer: NiFe: 6 nm) 47, a non-magnetic layer (Cu: 3 nm) 48, a pinnedlayer (pinned layer: NiFe: 3 nm) 49, an anti-magnetic film (Fe—Mn: 10nm) 50, and a protection layer (Hf: 5 nm) 51 successively.

[0079] To detect the field intensity difference using theabove-mentioned structure, the magnetization direction of the pinnedlayer 44 which is a component of the first spin valve element 34 isdifferentiated angularly from the magnetization direction of the pinnedlayer 49 which is a component of the second spin valve element 33 by 180degrees. To realize the difference, the blocking temperature of theantiferromagnetic films 45 and 50 which are components of two spin valveelements is differentiated each other by 20° C. or larger.

[0080] The magnetization direction of the pinned layers 44 and 49 can beprescribed to be parallel or antiparallel with respect to a prescribedaxis (usually, in the direction parallel to the line β shown in FIG. 1A)by exchange interaction from the antiferromagnetic films 45 and 50. Theparallel magnetization direction or antiparallel magnetization directioncan be prescribed by applying an external field. The exchangeinteraction is dependent on the temperature, and demagnetized above acertain temperature. The temperature is called as blocking temperature.

[0081] As described herein above, the magnetization of a pinned layercan not be prescribed above the blocking temperature. Therefore, if theblocking temperature of the antiferromagnetic films 45 and 50 which arecomponents of each spin valve element is different in the laminated spinvalve elements 33 and 34, the magnetization of a pinned layer can beprescribed by controlling the temperature when an external field isapplied.

[0082] The blocking temperature is different depending onantiferromagnetic material such as NiFe, NiMn, IrMn, and NiO, further,the blocking temperature of the same material is different depending oncomposition and deposition condition. The difference is controllable andit is easy to differentiate the blocking temperature by 20° C. orlarger. The blocking temperature difference of 20° C. or larger allowseasy pinned layer magnetization inversion of 180 degrees, that is, thereis no probelm in magnetize operation.

[0083] From the reason described herein above, it is understandable thatthe magnetization direction of the pinned layer 44 which is a componentof the first spin valve element 34 and the pinned layer 49 which is acomponent of the second spin valve element 33 is changed by about 180degrees each other (to antiparallel relation).

[0084] Next, the reason why the field intensity difference can bedetected by changing the magnetization direction of the pinned layer 44of the first spin valve element 34 and the pinned layer 49 of the secondspin valve element 33 by about 180 degrees (to antiparallel relation) isdescribed.

[0085]FIG. 6A shows the magnetization state of a spin valve element(giant magnetoresistive element in a broader sense). The magnetizationdirection of the pinned layer 67 is antiparallel to Y-axis(perpendicular field direction). The medium layer 66 consists of anon-magnetic material (Cu). The soft magnetic layer (free layer) 65having magnetization state parallel to X-axis is located on the mediumlayer 66. When a field (perpendicular field component: perpendicular tothe plane of a recording medium) 68 is applied to this layer, themagnetization 91 is turned to α direction or β direction depending onthe direction of the field. If the magnetization 91 turns in αdirection, then it is oriented toward the direction parallel to themagnetization direction of the pinned layer 67. On the other hand, ifthe magnetization 91 turns in β direction, then it is oriented towardthe direction antiparallel to the magnetization of the pinned layer 67.Based on the principle of the spin valve element, the parallel stategives a low electrical resistance and the antiparallel state gives ahigh electrical resistance.

[0086] Next, the sensitivity to a field gradient in the structure simplycomprising two spin valve elements piled up one above the other asdescribed herein above is examined.

[0087] As shown in FIG. 6B, two spin valve elements having a mediumlayer 66-1 and medium layer 66-2 respectively are piled up one above theother (elements are shown schematically apart each other for the purposeof description in the drawing), and it is assumed that a field 69 isapplied to the first element and a field 70 directing to the oppositedirection is applied to the second element. As shown in the drawing, themagnetization of the soft magnetic layer 65-1 turns in β direction, andon the other hand, the magnetization of the soft magnetic layer 65-2turns in α direction. The magnetization direction of the soft magneticlayer 65-1 is antiparallel to the magnetization direction of the pinnedlayer 67-1, and on other hand, the magnetization direction of the softmagnetic layer 65-2 is parallel to the magnetization direction of thepinned layer 67-2. Mere difference in polarity between the externalfield 69 and 70 only results in the difference in resistance between theelements, and the add resistance is not changed (precisely to say, theadd resistance changes slightly due to quality dispersion of theelement). In other words, the structure shown in FIG. 6B is notsensitive to the field gradient.

[0088] However, as shown in FIG. 6C, in the case of antiparallelmagnetization direction of the pinned layer 67-1 and pinned layer 67-2,the field 69 is applied to the first element and an opposite field 70 isapplied to the second element, then magnetization turns as describedherein above, and thereby both becomes antiparallel (high resistance) tothe magnetization direction of the pinned layers 67-1 and 67-2respectively. As a result, the add resistance of two elements increases.On the other hand, in the case that the external field 69 and theexternal field 70 are both oppositely oriented, because themagnetization of the soft magnetic layer turns in the oppositedirection, both resistance decreases.

[0089] However, if the field 69 and field 70 are both parallel, becausethe magnetization of the soft magnetic layers 65-1 and 65-2 both turnsin the same direction, the magnetization direction of the soft magneticlayers 65-1 and 65-2 is antiparallel and parallel to the magnetizationdirection of the pinned layers 67-1 and 67-2 respectively. As a result,add resistance does not change. As described herein above, byprescribing the direction of the pinned layer magnetization of the firstelement and of the pinned layer magnetization of the second element inantiparallel each other, the spin valve element structure is renderedsensitive so that the resistance is changed only when fields ofdifferent opposite polarity are applied to two elements.

[0090] When a field gradient is applied between two spin valve elements,a situation is formed, and this situation is the same as that describedherein above, namely, the situation formed when different externalfields are applied to two elements. The difference causes a change inadd resistance of two elements based on the reason described hereinabove. The change is detected as the change in current or voltage, thatis obvious from the above-mentioned reason.

[0091] This example is featured by antiparallel (about 180 degrees)magnetization direction of the pinned layers 44 and 49 as shown in FIG.1D.

[0092] Alternatively to specify the magnetization direction of thesepinned layers, a method in which exchange coupling between a highcoercive force film such as α-Fe₂ O₃ film or CoPt film and ferromagneticfilm is used is known. In this case, high coercive force films aredeposited instead of the antiferromagnetic films 45 and 50 (piled up atthe same position).

[0093] In the present invention, because two spin valve elements arepiled up, elements having a difference in corrosive force between theseelements of 100 Oe or larger are used. Because of the difference incoercive force, the magnetization direction can be prescribed byreducing successively magnetization field. Thereby, the magnetizationdirection of a pinned layer is prescribed arbitrarily (in the presentinvention, in antiparallel). The larger the difference in coercive forceis, the easier the magnetization is, however, the difference of 100 oeor higher is sufficient for practical application. It is well known thatthe difference in coercive force is controlled by controlling material,film composition, deposition temperature, and deposition velocity. Theabove-mentioned operations are utilized to prescribe the magnetizationdirection of pinned layera to be in antiparallel, and applied to thepresent invention.

[0094] A field gradient detection means comprising two functional thinfilms (spin valve elements 33 and 34) shown in the FIG. 1D isincorporated in a magnetic head slider 2 which is similar to aconventional magnetic head slider as shown in FIG. 3. The magnetic headslider 2 is provided with a recording means according to a prescribedmanner. A perpendicular magnetic recording medium having the axis ofeasy magnetization in the perpendicular direction to the film plane isused as the recording medium 11. The magnetic head slider 2 is supportedby a suspension 7 and arm 4. A rotary actuator 3 is used for positioningthe magnetic head slider 2 and recording medium. Other components suchas a motor for rotating the recording medium, a circuit board forprocessing electric signals, and an electric circuit for controlling thewhole apparatus are used to complete the recording apparatus though theyare not shown in the drawing.

[0095] By applying the field gradient sensing system which is the maincomponent of the reproducing apparatus of this invention, the outputsignal is rendered Gaussian shaped regardless of using a perpendicularmedium as a recording medium. Hence, the same signal processing circuitas used in a reproducing apparatus which uses a conventional recordingmedium having a longitudinal magnetization film can be used. The signalprocessing circuit is featured in that the circuit scale is smallbecause of reduced number of signal detection points and the circuit isexcellent in high speed capacity. Therefore, the increased recordingdensity does not cause any process time loss for processing signals.

[0096] The above-mentioned effect is obtained only by the presentinvention and is realized by applying the field gradient detection meansprovided with piled up two functional thin films (spin valve elements 33and 34) shown in FIG. 1D to the reproducing means for reproducingmagnetic information generated from a perpendicular magnetization film.

[0097] To describe more clearly this point, the present invention isdescribed with reference to FIG. 7A and FIG. 7B.

[0098]FIG. 7A is a sectional view (cross section in the plane parallelto the line β in FIG. 1A) of a field gradient detection means providedwith two functional thin films 33 and 34 and a perpendicularmagnetization film. In the perpendicular magnetization film 11, themagnetic state turns from an upward magnetic state 81 to a downwardmagnetic state 82 at the position where information “1”is located, andthe information is detected based on the existence of a transition 80.

[0099] It is assumed that the first functional thin film 33 and thesecond functional thin film 34 are positioned just above the transition80 of the medium. Magnetic fluxes are generated from each domain in thearrow direction shown in the drawing, and these magnetic fluxespenetrate into two functional thin films (in detail, soft magneticlayers which are components of spin valve elements).

[0100] Because of antiparallel magnetization state on the right vs. leftside separated at the boundary of transition 80, two fields which act ontwo functional thin film are antiparallel. In other words, a differenceof the field is caused between two functional thin films. The differencecauses a change in add resistance of two functional thin films becauseof the reason described herein above, and the change is detected as anelectric signal. Angular directional turning of the magnetizations 81and 82 results in directional turning of magnetic flux which acts on twofunctional thin films. This turning causes resistance change in reverseto the above-mentioned manner (increase or decrease).

[0101] However, on a place where there is no transition just under thefirst functional thin film 34 and the second functional thin film 33 asshown in FIG. 7B, equal and weak magnetic fluxes (stray field decreasesdue to demagnetization from domain itself) penetrate to two functionalthin films, no electric signal is therefore generated.

[0102] As described herein above, only when a difference of the fieldfrom a magnetic recording medium namely field gradient is given,electric resistance of two functional thin films changes. Because thechange is differently incremental resistance or decremental resistancedepending on the magnetic state of polarity of transition, Lorentzianpulse electric signal is obtained. Based on this feature, it is possibleto process signals using the same signal processing as usedconventionally (longitudinal magnetization film) regardless of using ofa perpendicular magnetization film.

[0103] The above-mentioned example involves the generally used structureof a spin valve element. However, the present invention is also realizedby using other spin valve element structure.

Second Example

[0104] Dual MR head described in THEORY OF MAGNETIC RECORDING by H. NEALBERTRAM on pages from 194 to 199 has been known as another structure fordetecting magnetic gradient generated by perpendicular field. In thisstructure, as shown in FIG. 4A and FIG. 4B, two magnetoresistiveelements 61 and 63 are piled up with interposition of an insulator layeror a high resistance film 62, the fields generated by the currentmagnetize the magnetoresistive elements asymmetrically. The asymmetricalmagnetization is determined by current intensity, element width, anddistance between magnetoresistive elements, and easily estimated basedon the soft adjustment layer (SAL) magnetoresistive sensor theory.

[0105] Though the above-mentioned structure is very simple, thestructure is disadvantageous in that sensitivity is low because thefunctional thin film functions based on magnetoresistive effect.Therefore, in the recording density range exceeding 10 Gb/in²where theperpendicular magnetization film is required, the reproducing output isinsufficient. Though magnetization asymmetry causes no problem ofsymmetry property of amplitude (no difference between plus signal andminus signal), the magnetization asymmetry causes the change in symmetryof pulse on the time axis. This phenomenon is not described in theabove-mentioned disclosed art. This problem of symmetry of pulse on thetime axis is due to the property of magnetoresistive element that thesensitivity of two magnetoresistive elements change reversely (high andlow) depending on the magnetization asymmetry. This phenomenon resultsin reproduction of a pulse having a wide skirt when magnetic informationis positioned on the side of magnetoresistive element of highersensitivity, and on the other hand, results in reproduction of a pulsehaving a narrow skirt when magnetic information is positioned reversely.

[0106] The interference between neighboring signals becomes remarkablewith increasing high density recording. When, if a signal has nonlineardistortion, following signal processing can not be performed. To avoidthis trouble, two magnetoresistive elements having the same sensitivitymay be used, however, because of inevitable some allowance ofsensitivity in manufacturing and accuracy of supplied current (includingcontrol of external factors such as temperature), such factors cause theproblem.

[0107] Because spin valve elements are used in the present invention,the present invention is applied to dual MR head without any problem.Because magnetization of a pinned layer is prescribed in one directionby a antiferromagnetic film in the spin valve structure, the problem ofasymmetry is not involved. Such excellent structure can not be derivedfrom the above-mentioned conventional art.

Third Example

[0108] Another example for realizing excellent reproducing function froma perpendicular magnetization film using two spin valve elements isdescribed hereinafter. In this example, the first spin valve element 34and the second spin valve element 33 are maintained in electricinsulated condition. As shown in FIG. 5A, electrodes 71 and 73 and 72and 74 are connected to the respective spin valve elements. These twopairs of electrodes are electrically insulated.

[0109] To maintain two spin valve elements in electrically insulatedcondition, an antiferromagnetic oxide film 52 is inserted between twospin valve elements 33 and 34 as shown in the cross sectional structureof FIG. 5B. NiFe alloy films 44 and 49 are deposited on the top andbottom surface of the antiferromagnetic oxide film 52, which is servedas a pinned layer. On the outside surface, Cu medium layers with athickness of 3 nm (non-magnetic layer) 43 and 48, and further NiFe alloyfilms with a thickness of 3 nm 42 and 47 are deposited. The NiFe alloyfilms 42 and 47 are soft magnetic films and served as a free layer of aspin valve element. To improve the function as a free layer, Hf films 41and 46 are deposited additionally on the outside surface. The Hf film isserved also as a protection film.

[0110] As described herein above, each electrode may be insulated withan antiferromagnetic oxide film 52 to maintain the first spin valveelement and the second spin valve element in electrically insulatedcondition. In detail, antiferromagnetic oxide films 52 are providedbetween the electrodes 71 and 72 and between the electrodes 73 and 74 toelectrically insulate. In this case, the process is simplified. By theway, in the above-mentioned structure, because the magnetization ofpinned layers 44 and 49 are specified by free layers 42 and 47consisting of common material (NiFe alloy film), it is impossible toprescribe the magnetization direction of the first spin valve element 34and the second spin valve element 33 in antiparallel. To prevent theproblem, the electrodes are insulated.

[0111] Using such structure, it is possible to reproduce recordedinformation from a perpendicular magnetization film by applyingso-called differential operation, in which output electrodes 72 and 74and output electrodes 71 and 73 are connected to amplifier circuits ofdifferent polarity as shown in the circuit diagram of FIG. 5C andrespective outputs are synthesized. Output is obtained finally only whenoutputs of different polarity are detected from two spin valve elements,this fact explains the reason. This state is equivalent to the stateshown in FIG. 7A and FIG. 7B, and based on this reason, it is possibleto reproduce recorded information from a perpendicular magnetizationfilm.

[0112] This example is featured in that the effect of thermalfluctuation is removed by differential operation circuit because thermalfluctuation affects the respective elements commonly if it occurs. Thefeature allows this method to be applied to contact recording which islikely to be involved in disturbance though the number of electrodesincreases.

[0113] Reproducing function is realized by a method in which any one ofthe above-mentioned reproducing means is provided to a magnetic headslider, and a part of which is provided at least on the air bearingsurface near the perpendicular magnetization recording medium surface.

[0114] When, as shown in FIG. 8, the soft magnetic pattern 38 isprovided on a place near the first and second spin valve elements 33 and34 and distant from the air bearing surface. By providing the softmagnetic pattern, a magnetic circuit is formed between the spin valveelement 33 and the spin valve element 34. The magnetic circuit iseffective for inducing efficiently the magnetic flux from themagnetization 81 and magnetization 82 in the recording medium 11. Ifthere is no magnetic pattern, the magnetic flux flows mostly from theside where two spin valve elements are located in parallel each other tothe neighboring element. However, if a magnetic circuit is formed on theside which is distant from the medium surface, the magnetic flux flowstoward the magnetic circuit. As a result, the magnetic flux flows intomore area of the elements, and the output is obtained efficiently.

Fourth Example

[0115] In this example, to detect the field intensity difference at theposition distant spatially, two giant magnetoresistive elements havingthe structure as described herein under are piled up. The example isdescribed with reference to a sectional view of FIG. 9.

[0116] First, a primary film (Hf: 5 nm) 41 is piled on a substrate, andan antiferromagnetic film (Fe—Mn: 10 nm) 45, and a magnetic film (firstferromagnetic film: NiFe alloy: 6 nm) 44 are piled up successively,thereafter an Ru film 56 having a thickness of 0.7 nm is deposited, andfurther a magnetic film (second ferromagnetic film: NiFe alloy film: 3nm) 57 is deposited.

[0117] On the film 57, a non-magnetic film (Cu: 3 nm) 43 is deposited,and then a soft magnetic film (third ferromagnetic film: NiFe alloyfilm: 6 nm) 42 which functions as a free layer is deposited. Thesesuccessively deposited films constitute a first spin valve element (agiant magnetoresistive element or functional thin film in a broadersense of the term) 34.

[0118] Next, for forming a second spin valve element 33, a soft magneticfilm (fourth ferromagnetic film: NiFe alloy film: 6 nm) 47 whichfunctions as a free layer is deposited on a spacer layer 46, and on it anon-magnetic film (Cu: 3 nm) 48, and a magnetic film (fifthferromagnetic film: NiFe alloy film: 3 nm) 49 which function as a pinnedlayer is deposited. On it an antiferromagnetic film (Fe—Mn: 10 nm) 53and a protection layer (Hf: 5 nm) 51 are deposited.

[0119] This example is featured in that after deposition of the magneticfilm (first ferromagnetic film: NiFe alloy film: 6 nm) 44, the Ru film56 with a thickness of 0.7 nm is deposited, and the magnetic film(second ferromagnetic film: NiFe alloy film: 3 nm) 57 is deposited. Thisstructure is described in Digests of INTERMAG '96 AA-04 by V. S.Speriosu et al. In this literature, it is described that themagnetization direction of ferromagnetic films between which the Ru filmis sandwiched is antiparallel, the magnetization direction of theferromagnetic film having a thicker thickness (to say precisely, higherproduct of saturation magnetization and film thickness) is coincidentwith the external field. This structure is featured in that the coerciveforce of the total magnetic films between which the Ru film issandwiched is increased, and the magnetostatic effect on the external isreduced. Application of this structure to a free layer or a pinned layerof a spin valve element is suggested based on these features.

[0120] In this example, this structure is applied to a pinned layer, butthe purpose of the present invention is different from that described inthe above-mentioned literature. In detail, in this example, two elementsare provided at the positions distant spatially each other to measurefield intensity simultaneously, and the difference in the fieldintensity is detected as an output difference to measure the fieldgradient. To realize this mechanism, in this example, an elementstructure in which the magnetization direction of pinned layers of piledup two spin valve elements is antiparallel is disclosed. Further, torealize this structure, the example described the structure in which theproperty of an Ru film is utilized. To clarify the novelty, it isimportant to understand the requirement of antiparallel magnetization ofpinned layers, this point was described in detail in the description ofthe first example with reference to FIG. 6A and FIG. 6C.

[0121]FIG. 10A and FIG. 10B are sectional views for describing themagnetization direction of the magnetic film which is required torealize the present invention. The magnetization direction of themagnetic film (first ferromagnetic film) 44 of the first spin valveelement 34 shown in FIG. 10A is regarded as a reference, and themagnetization direction is assumed to be left facing to the paper plane,then it is required that the magnetization direction of the secondferromagnetic film 57 is right. The magnetization direction of themagnetic film (fifth ferromagnetic film) 49 of the second spin valveelement 33 shown in FIG. 10B is required to be left. The soft magneticfilms 42 and 47 which function as a free layer have an inclination of 90degrees with respect to the pinned layer magnetization (it is realizedby magnetizing the permanent magnet 35 shown in FIG. 1B and FIG. 1C) sothat the magnetization direction both turns in the same direction whenan external field is applied.

[0122] The magnetization structure of the above-mentioned magnetic film(pinned layer) is realized by magnetization processing shownrespectively in FIG. 11A1 FIG. 11A2, FIG. 11B1, and FIG. 11B2. FIG. 11A1shows the structure after film forming of the first spin valve element34. In this structure, the magnetization direction of respectivemagnetic films is not yet prescribed. As shown in FIG. 11A2, heattreatment is carried out at a temperature around the blockingtemperature of the antiferromagnetic film 45 under application of anexternal field 61.

[0123] Because magnetization of the first ferromagnetic layer 44 and thesecond ferromagnetic layer 57 is coupled strongly in antiparallel, bothlayers 44 and 57 behave together as one magnetic film layer under anormal condition. The ferromagnetic layer having the higher product ofthe film thickness and saturation magnetization is predominant to theexternal field 61 out of two ferromagnetic layers, and the magnetizationdirection of the predominant ferromagnetic layer is parallel to theexternal field 61. As a result, the magnetization direction of the layerhaving the lower product of the film thickness and saturationmagnetization is directed opposite to the external field 61. In thisexample, the magnetization of the first ferromagnetic layer 44 isdirected in the direction of the external field 61 and the magnetizationof the second ferromagnetic layer 57 is directed in the directionopposite to the external field 61. The magnetization of the firstmagnetic film 44 is fixed in the direction of the external field 61 dueto exchange coupling on the interface of the antiferromagnetic layer 45.This principle is the same as involved in the conventional spin valveelement.

[0124] In this example, because the magnetic film 44 is in contact withthe Ru 56 which causes antiferromagnetic coupling in extremely thin filmcondition, the magnetization direction of the second magnetic film 57which is in contact with the reverse interface is antiparallel withrespect to the external field 61. This phenomenon is described in theabove-mentioned literature.

[0125] Similarly, application of the external field 61 to the structureafter film forming of the second spin valve element 33 shown in FIG.11B1 results in the state shown in FIG. 11B2. This state is easilyunderstandable from the fact that the magnetization of the fifthmagnetic film 49 is fixed in the direction of the external field 61 dueto the effect of exchange coupling from the antiferromagnetic layer 53.

[0126] In the structure shown in FIG. 11A2 and FIG. 11B2, the spacer 46is used commonly, on both sides of the spacer 46 the third magnetic film42 and fourth magnetic film 47 which function as a free layer arelocated. These magnetic films can be turned freely by an external fieldas described hereinbefore. These magnetic films are located on themagnetic film 57 (second magnetic film) and the magnetic film 49 (fifthmagnetic film) which function as a pinned layer with interposition ofthe Cu films 43 and 48. Because the magnetization direction of themagnetic film 57 (second magnetic film) and the magnetic film 49 (fifthmagnetic film) is antiparallel each other based on the above-mentionedprinciple, the first spin valve element 34 and the second spin valveelement 33 perform differential function.

[0127] For structuring the above-mentioned magnetization structure,emphasis is placed on making the film thickness of the second magneticfilm 57 thin relatively to the film thickness of the first magnetic film44. By structuring the magnetic films as described herein above, themagnetization direction of the first magnetic film 44 is directedpreferentially in parallel to the external field direction 61 (in themacro view point, magnetized so that magnetostatic energy is reduced),and the magnetization direction of the second magnetic film 57 locatedon the side in contact with the free layer 42 is directed inantiparallel to the external field direction 61. The principle describedherein above can be estimated easily from the above-mentionedliterature, but there is a problem in application of this principle tothe dual type element structure of the present invention. In detail, thecoercive force of the pinned layer comprising the first magnetic film44, Ru film 56, and second magnetic film 57 is insufficient.

[0128] Inventors of the present invention are aware of a knowledge fromexperiments that equalization of fixing force of the pinned layermagnetization of two elements is essential to secure symmetry of theoutput for using the dual type element structure.

[0129] For the purpose of secure symmetry, in the present invention, themagnetization direction of the first magnetic film 44 and the fifthmagnetic film 49 are fixed by the antiferromagnetic films 45 and 53. Thedifference of output between the first spin valve element and the secondspin valve element is eliminated. This novel art is not disclosed in theabove-mentioned known example, it is said that this art is a novel artpeculiar to the dual type element of the present invention.

[0130] This problem is solved also by using a ferromagnetic filmconsisting of high coercive force material such as Co—Pt instead of theantiferromagnetic films 45 and 53. In this case, the magnetizationdirection of the ferromagnetic film (equivalent to 45 and 53) isprescribed to be in parallel (equal) to the external field by performingmagnetization processing as shown in FIG. 11A1 FIG. 11A2, FIG. 11B1, andFIG. 11B2. Also in this case, the magnetization of the ferromagneticfilm and the pinned layer is exchange-coupled, and the magnetizationdirection is prescribed. Therefore, the desired spin valve elementstructure is structured like th above-mentioned structure. By providingan Ru film in the spin valve element, the magnetization direction of thepinned layer which is in contact with the non-magnetic Cu film isprescribed to be in antiparallel to the magnetization field. Thereby,the same function as that of the above-mentioned example can berealized.

[0131] In the above-mentioned example, a NiFe alloy film is used as themagnetic films 44 and 57, however alternatively a Co ally film which isa magnetic film may be used for the present invention without anyproblem. Similarly, Ta or oxide may be used for the protection film 51instead of Hf film without any problem in application of the presentinvention.

[0132] Further, to enhance the function of the first and second spinvalve elements, an extremely thin film of Co r NiFe may be provided onthe interface facing to the Cu layer or Ru layer, this method is appliedto the present invention without any problem. Therefore it is obviousthat these examples are included in the present invention.

[0133] The case that Ru is used for the first non-magnetic layer 56 isdescribed in the above-mentioned examples, however alternatively, anyone metal selected from a group including Ir, Rh, Cr, and Cu or any onealloy containing two or more alloy materials which results in strongantiferromagnetic layer coupling may be used instead of Ru, and it isconfirmed that these materials give the same effect as Ru.

[0134] A field gradient detection means comprising two functional thinfilms described hereinbefore is incorporated into a conventionalmagnetic head slider 2 shown in FIG. 3. In the magnetic head slider 2, arecording means is provided in the usual manner. A perpendicularmagnetic recording medium having an axis of easy magnetization inperpendicular direction to the film plane is used as the recordingmedium 11. The magnetic head slider 2 is supported by the suspensionmember 7 and arm 4. The magnetic head slider 2 and the recording mediumare positioned by the rotary actuator 3. A recording apparatus of thepresent invention is completed using other components such as a motorfor rotating the recording medium, circuit board for processing electricsignal, and electric circuit for controlling the whole apparatus, whichare not shown in the drawings. By applying the field gradient detectionmeans which is the main component of the present invention, reproducingsignal of Gaussian shape is obtained regardless of using a perpendicularmagnetic film medium as a recording medium. As a result, the same signalprocessing circuit as used for signal processing of a longitudinalmagnetization film recording medium is used successfully.

[0135] This signal processing circuit has a small number of signaldetection points and is a circuit of a small scale, and excellent inhigh speed performance. Signal processing causes no processing time lossregardless of increased recording density.

[0136] The above-mentioned effect can be obtained only by the presentinvention, and the effect is realized by applying the field gradientdetection means comprising piled up two functional thin films to a meansfor reproducing magnetic information generated from a perpendicularmagnetic film. To clarify this point, the example is described in detailwith reference to FIG. 12A and FIG. 12B. FIG. 12A shows a sectional view(sectional view along the plane parallel to the line β in FIG. 1) of thefield gradient detection means comprising piled up two functional thinfilms and the perpendicular magnetic film. In the perpendicular magneticfilm 11, the magnetization condition changes from upward magnetization81 to downward magnetization 82 at the position where the information“1” is located. Therefore information is read out based on the existenceof the transition 80.

[0137] It is assumed that the first functional thin film 65-1(equivalent to the first spin valve element 34) and the secondfunctional thin film 65-2 (equivalent to the second spin valve element33) are positioned just above the transition 80 on the perpendicularmagnetization film, a magnetic flux is generated in the direction asdescribed in the drawing from each domain, and the magnetic fluxpenetrates into two functional thin films (in detail, the soft magneticlayer which is a component of a spin valve element). Because the rightand left magnetization states are different and antiparallel withrespect to the border of the transition 80, fields acting on twofunctional thin films are antiparallel each other. It is understandablethat field difference is generated between two functional thin films. Asa result, add resistance of two functional thin films changes based onthe reason described herein above, and the change is detected as anelectric signal. When the direction of the magnetization 81 and 82 isreversed, then the direction of the magnetic flux is also reversed. As aresult, resistance change opposite to the above-mentioned case occurs(increase or decrease of the resistance).

[0138] However, on a place where there is no transition just under thefirst functional thin film 65-1 and the second functional thin film 65-2as shown in FIG. 12, an equal and weak magnetic flux (stray fielddecreases due to demagnetization from domain itself) penetrates into twofunctional thin films, and no electric signal is generated.

[0139] As described herein above, the resistance changes only when thefield difference from a medium between two functional thin films namelythe field gradient is caused. Because the change results in resistanceincrement or resistance decrement depending on the magnetization stateof a transition position, Lorentzian pulse electric signal is obtained.Based on this feature, the same signal processing as used for aconventional longitudinal magnetization film is used successfullyregardless of using a perpendicular magnetization film.

Fifth Example

[0140] The above-mentioned examples provided with generally used spinvalve elements are described. However, other spin valve elementstructures may be applied to realize the present invention. For example,an element having a pinned layer of the second spin valve element 33shown in FIG. 13 comprising the fifth magnetic film 49, the Ru film 54,and the sixth magnetic film 55 with the magnetization direction fixed bythe antiferromagnetic film 53 is included in the scope of the presentinvention. In this example, other basic element structure, magnetizationstructure, and electrode structure is the same as the above-mentionedexamples. In this example, the structure of the pinned layer is the sameas that of the first spin valve element. Therefore the output of thefirst spin valve element 34 and the second spin valve element 33 iscompletely symmetrical, and excellent reproducing processing isperformed.

[0141] To apply the spin valve element which uses the two Ru films 54and 56 to the present invention, it is required that the magnetizationdirection of the second magnetic film 57 and the magnetization directionof the fifth magnetic film 49 are antiparallel each other. To realizethe antiparallel magnetization direction by applying an external field,it is required that the product of the film thickness and saturationmagnetization of the first magnetic film 44 which is in contact with theantiferromagnetic film 45 is larger than the product of the filmthickness and saturation magnetization of the second magnetic film 57,and also the product of the film thickness and saturation magnetizationof the sixth magnetic film 55 which is in contact with theantiferromagnetic film 53 is smaller than the product of the filmthickness and saturation magnetization of the fifth magnetic film.

[0142] A hard magnetic film (ferrimagnetism, forromagnetism) which hasthe same magnetization direction as that of an external field is used atthe same position instead of the antiferromagnetic film 53 without anyproblem. Elimination of the ferromagnetic film does not cause anyproblem to realize the present invention. Though this example is aspecial case, this example also involves the same principle to solve theproblem on which the present invention addresses, therefore this exampleshould be included in the scope of the present invention.

[0143] Any one of the above-mentioned reproducing means is provided in amagnetic head slider, and a portion of the reproducing means is locatedon the air bearing surface at least near a perpendicular magneticrecording medium surface, and thus reproducing function is realized.

[0144] According to the present invention described hereinbefore,reproducing signal is Gaussian shaped regardless of using aperpendicular magnetic film as a recording medium. Based on this effect,the same signal processing circuit as used for reproducing alongitudinal magnetization film recording medium is used successfully.Because such signal processing circuit has the small number of signaldetection points, the circuit scale is small, and the signal processingcircuit is excellent in high speed performance. As a result, there is noprocessing time loss in signal processing regardless of increasedrecording density.

[0145] The above-mentioned effect can be obtained only by the presentinvention, and realized by applying a detection means comprising piledup two spin valve elements to a reproducing means of magneticinformation obtained from a perpendicular magnetization film. Based onthe effect described hereinabove, a high density storage apparatushaving a recording density of 10 Gb/in² or more using a perpendicularmagnetization film is realized.

[0146] The reproducing head of this invention is effective also fordensification of longitudinal magnetization film recording. The reasonis described herein under. In the improvement of linear density of alongitudinal magnetization film, the reproducing resolution is specifiedby the distance of the shield in the case of a conventionalmagnetoresistive reproducing head and spin valve head. In other words,it is required that the distance of the shield is narrow for high linerdensity. However, it is very difficult for narrow distance of the shieldthat the multi-layered complex structure such as a spin valve is locatedbetween shields and the electric insulation between the shield and thespin valve is maintained consistently. On the other hand, because asimple spacer layer specifies the resolution and electric insulation isnot required in the method of the present invention, the high lineardensity is realized easily.

What is claimed is:
 1. A magnetic head comprising: a first spin valveelement; a second spin valve element; and a non-magnetic spacer layerformed between the first spin valve element and the second spin valveelement; the first spin valve element including: a firstantiferromagnetic film a first ferromagnetic film; a first non-magneticfilm; a second ferromagnetic film; a second non-magnetic film of whichmagnetization direction can be rotated in respect to an externalmagnetic field; and a first soft magnetic film; the second spin valveelement including: a second antiferromagnetic film; a thirdferromagnetic film; a third non-magnetic film; and a second softmagnetic film of which the magnetization direction can be rotated inrespect to an external magnetic field; wherein: the magnetizationdirection of the first ferromagnetic film and the magnetizationdirection of the second ferromagnetic film are in an antiparallel state;the magnetization direction of the second ferromagnetic film and themagnetization direction of the third ferromagnetic film are in anantiparallel state; and the first soft magnetic film and the second softmagnetic film are arranged to be symmetrical with respect to thenon-magnetic spacer layer.
 2. A magnetic head according to claim 1 ,wherein said first non-magnetic medium layer consists of any one ofmetal layers selected from a group of Ru, Rh, Ir, Cr, and Cu or consistsof an alloy containing some of these metals.
 3. A magnetic headaccording to claim 1 , wherein said second non-magnetic film and saidthird non-magnetic film comprise a Cu layer.
 4. A magnetic headaccording to claim 1 , wherein the product of the film thickness andsaturation magnetization of said first ferromagnetic film is larger thanthe product of the film thickness and saturation magnetization of saidsecond ferromagnetic film.
 5. A magnetic head according to claim 1 ,wherein the magnetization direction of said first ferromagnetic film andsaid third ferromagnetic film is prescribed to be in the same direction.6. A magnetic head according to claim 1 , wherein the magnetizationdirection of said first ferromagnetic film and said third ferromagneticfilm is prescribed by antiferromagnetic films or hard magnetic filmswhich are respectively in contact with both said first ferromagneticfilm and said third ferromagnetic film.
 7. A magnetic head according toclaim 1 in which a film thickness of the second ferromagnetic film issmaller than a film thickness of the first ferromagnetic film.
 8. Amagnetic head comprising: a first spin valve element; a second spinvalve element; and a non-magnetic spacer layer formed between the firstspin valve element and the second spin valve element; the first spinvalve element including: a first antiferromagnetic film a firstferromagnetic film; a first non-magnetic film made of Ru; a secondferromagnetic film; a second non-magnetic film of which themagnetization direction can be rotated in respect to an externalmagnetic field; and a first soft magnetic film; the second spin valveelement including: a second antiferromagnetic film; a thirdferromagnetic film; a third non-magnetic film; and a second softmagnetic film of which the magnetization direction can be rotated inrespect to an external magnetic field; wherein: the magnetizationdirection of the second ferromagnetic film and the magnetizationdirection of the third ferromagnetic film are in an antiparallel state;and the first soft magnetic film and the second soft magnetic film arearranged to be symmetrical with respect to the non-magnetic spacerlayer.
 9. A magnetic head according to claim 8 , wherein said firstnon-magnetic medium layer consists of any one of metal layers selectedfrom a group of Ru, Rh, Ir, Cr, and Cu or consists of an alloycontaining some of these metals.
 10. A magnetic head according to claim8 , wherein said second non-magnetic film and said third non-magneticfilm comprise a Cu layer.
 11. A magnetic head according to claim 8 ,wherein the product of the film thickness and saturation magnetizationof said first ferromagnetic film is larger than the product of the filmthickness and saturation magnetization of said second ferromagneticfilm.
 12. A magnetic head according to claim 8 , wherein themagnetization direction of said first ferromagnetic film and said thirdferromagnetic film is prescribed to be in the same direction.
 13. Amagnetic head according to claim 8 , wherein the magnetization directionof said first ferromagnetic film and said third ferromagnetic film isprescribed by antiferromagnetic films or hard magnetic films which arerespectively in contact with both said first ferromagnetic film and saidthird ferromagnetic film.
 14. A magnetic head according to claim 8 inwhich a film thickness of the second ferromagnetic film is smaller thana film thickness of the first ferromagnetic film.